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Thread: Define TOP & BOTTOM of a framing family

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    Member TRWhitehead's Avatar
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    Define TOP & BOTTOM of a framing family

    I'm trying to create (pretty unsuccessfully) to build a tapered wood joist family. I've got it set up to taper based on slope (type parameter for rise/run then atan function to get angle) but the way the element needs to be placed in elevation is based on the low end of the slope or the bottom of the bottom chord. The grand plan is to use this to frame a wood roof using the beam system tool (big spaces with members spaced at 2'-0" OC). The joists will actually be bidder designed so I only want to show a top and bottom chord, no need to model the web members. I could do it as a truss I guess but I'm afraid I'd have to attach each truss to the roof deck above to get the slope correct.

    Here's the problem. How can I set the "top" of the element to be based on the low end of the top chord? The reason being that is the constant for these, not the high end. And with a beam system I can only effectively place it based on the "top" of the member or an offset from there.

    Define TOP & BOTTOM of a framing family-condition.pngDefine TOP & BOTTOM of a framing family-family.png

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    try defining the top and bottom with reference planes.

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    Member TRWhitehead's Avatar
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    Quote Originally Posted by Alex Cunningham View Post
    try defining the top and bottom with reference planes.
    I tried that but when placed, the top is always the absolute top of the element, which is the high end of the tapered joist.

    Unfortunately, what is fairly constant is that low end elevation. I was hoping to use beam systems so aligning it based on the bottom won't work (you can't have beam systems bottom justified as far as I can tell). An offset won't work very well as the total height will vary pretty often and might be some really odd numbers because of slope.
    Last edited by TRWhitehead; April 3rd, 2012 at 02:34 PM.

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    Try changing the refplane which defines the Origin

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    Member TRWhitehead's Avatar
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    Martijn,

    I did that yesterday in between deadlines and although it changed how the member was located in elevation I can't figure out how it defines the top and bottom. Seemed to be kinda random. Do you have some insight into that?

    Here's the problem. The sloped joist/truss I need doesn't have a roof to attach to in all cases. Beam systems require that they are defined by "top" or offset from top. But the way this roof and joist interact the elevation of the high side varies and the low side is pretty consistent. So I need to build a sloped member (slope defined by a trig function and rise/run numbers) that has its "top" defined at the low end of the top chord. I may have some time to play with it today. I'll see if I can come up with the math.

    And as a side note, if you are in the Netherlands, how do you know about Blue Bell ice cream from Brenham, Texas? (I'm originally from Austin)

    THanks,
    Tom

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    Quote Originally Posted by TRWhitehead View Post
    And as a side note, if you are in the Netherlands, how do you know about Blue Bell ice cream from Brenham, Texas? (I'm originally from Austin)
    Thats a long story... Which can be seen here: http://www.revitforum.org/out-there/...html#post28717

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    Quote Originally Posted by TRWhitehead View Post
    Martijn,

    I did that yesterday in between deadlines and although it changed how the member was located in elevation I can't figure out how it defines the top and bottom. Seemed to be kinda random. Do you have some insight into that?

    Here's the problem. The sloped joist/truss I need doesn't have a roof to attach to in all cases. Beam systems require that they are defined by "top" or offset from top. But the way this roof and joist interact the elevation of the high side varies and the low side is pretty consistent. So I need to build a sloped member (slope defined by a trig function and rise/run numbers) that has its "top" defined at the low end of the top chord. I may have some time to play with it today. I'll see if I can come up with the math.

    And as a side note, if you are in the Netherlands, how do you know about Blue Bell ice cream from Brenham, Texas? (I'm originally from Austin)

    THanks,
    Tom
    Well, I can't really reproduce your problem here. Maybe post the family for reference?
    About the icecream: blame Dan...

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